1. Field of the Invention
The present invention generally pertains to downhole oilfield equipment, and more particularly to improved inflatable packers.
2. Description of the Related Art
It is known that there are mainly two kinds of inflatable packers, namely, slat type and weave or cable type. The slat type inflatable packers usually have a high pressure rating and a large expansion ratio. However, in general the slat type inflatable packers are not recommended for open hole applications, especially with a high expansion, because the slats do not have enough flexibility to conform to open hole profiles with potential irregularities. As a result, the inner tube or bladder of the slat type packer may be extruded through the openings between the slats. On the other hand, weave type structures will equip the packer element with enough compliance to conform to the well bore geometry, but they have a low pressure rating and a small expansion ratio. In addition to the structural design of an inflatable packer, the mechanical performance and reliability of inflatable packers depend in part upon the mechanical properties of the materials used.
As will become apparent from the following description and discussion, the present invention overcomes the deficiencies of the previous packers and constitutes an improved packer. In one aspect of the present invention, this is accomplished by the development of hybrid structures for through-tubing multiple-settable high-expandable inflatable packer elements which utilize unique features of slat type and weave type structures to achieve a much improved performance and compliance of the packer elements in open hole environments as well as cased hole environments. In another aspect of the present invention, improvement in the field of packers may be achieved by development of inflatable packer elements with high expansion ratios, high pressure ratings, high extrusion resistance, and good shape recovery after deflation by the use of materials from the fields of fiber reinforced composites and nanotechnology, including, for example, various fiber reinforced elastomers, polymers, and/or metals, and nanofiber, nanotubes, nanoparticle modified elastomers, polymers and/or metals. Details concerning these types of materials can be found, for example, in WO0106087, U.S. Pat. No. 6,102,120, and A. B. Dalton et al., Super-Tough Carbon—Nanotube Fibres, Nature, Vol. 423, 12 Jun. 2003, p. 703 (“Dalton”). The authors in Dalton outline their process of synthesizing single-walled nanotube (SWNT) fibers into 100 meter length bundles. These fibers can then be formed into a mesh or woven into other fibers as a rubber reinforcement. Nanotechnology materials exhibit superior properties over traditional materials, including greater strength, flexibility, elongation and compliance to irregular surfaces such as those found in open hole applications.